In 2004, Roland Emmerich, having already depicted the destruction of large parts of the world at the hands of aliens (“Independence Day”) and Godzilla (“Godzilla”), upped the ante by introducing a new villain: the weather. “The Day After Tomorrow” was less fun and, if such a thing is possible, less believable than his previous efforts, but now Emmercih (after detouring into prehistoric idiocy with “10,000 B.C.”) has chosen to double down on the Mother-Nature-as-terrorist angle with “2012,” a very long, very loud, and very stupid disaster flick that apparently accomplishes what it set out to do, which was to be long, loud, and stupid.

In the unlikely event that you are interested, here’s the basic story. The ancient Mayans predicted that the world would end in 2012 (no they didn’t, actually, but OK), and now modern science has determined that, son of a bee, they were right. Solar flares sending a surplus of neutrinos earthward are to blame; “The neutrinos are causing a physical reaction!” is typical of the scientific mumbo-jumbo deployed in Emmerich’s screenplay (co-written with Harald Kloser). These ambitious neutrinos will cause the Earth’s crust to become unstable, leading the tectonic plates to shift around willy-nilly, which will be bad news for everyone except surfers.

The scientist whose job is to breathlessly tell the president what’s going on — ideally by interrupting an important meeting of some kind — is Dr. Adrian Helmsley (Chiwetel Ejiofor). Through a wormy adviser named Anheuser (Oliver Platt), Adrian gets the ear of Pres. Wilson (Danny Glover), who, like many disaster-movie presidents, is noble and decent and African American. Wilson secretly informs the other world leaders — well, the important ones, anyway; screw you, India! — about the impending danger. Top-secret plans are made to prepare for the disaster. One key elements of the plan: whatever you do, don’t warn the people! You’ll just create panic.

Among the unwarned is Jackson Curtis (John Cusack), a failed novelist and divorced father who drives a limousine for a Russian billionaire living in Los Angeles. While vacationing with his two children in Yellowstone — which they drive to, the 20-hour trip passing without comment — Jackson meets a crazy mountain man named Charlie (Woody Harrelson, not really “acting”) who broadcasts his end-of-days conspiracy theories on the radio. Charlie tells Jackson that the end is nigh, and that the government has known for years. Jackson thinks Charlie might be telling the truth after he runs into a heavily protected military installation in the middle of Yellowstone. (And by “heavily protected” I mean there’s a chain-link fence that says “keep out,” and Jackson and the kids climb over it.) What are these Army guys monitoring out here in the middle of nature?

We’re about 45 minutes into the film before things really hit the fan, but when they do hit, they hit hard. Jackson’s limousine, apparently as indestructible as a tank but as easily maneuverable as a bicycle, speeds thrillingly through Los Angeles as it’s devastated by colossal earthquakes. To watch it, you’d think Jackson and his passengers will be the only survivors. Those passengers, by the way, are his children (Liam James and Morgan Lily), his ex-wife, Kate (Amanda Peet), and her new boyfriend, Gordon (Tom McCarthy). You think it’s rough having dinner with your ex and her new guy, imagine having to spend the apocalypse with them.

The thrust of the plot is that various people worldwide are trying to get to a place where it is believed they will be safe from the calamities. As is to be expected from the man who brought us “Independence Day,” this will be accomplished through extraordinary coincidences that bring the right characters together at exactly the right time, through imbuing them with unlikely skills (“a couple flight lessons” is all you need to be able to fly a plane!), and through a wanton disregard for the laws of physics.

Along the way there are numerous scenes of awe-inspiring destruction, much of which is genuinely impressive in terms of size and scale. Makers of disaster movies even 10 years ago could only have dreamed of creating this much mayhem so realistically. Emmerich knows how to parcel it out effectively, too. I mean, it’s not just the destruction we’re talking about. You could pull back to a shot from outer space and show the Earth exploding into trillions of pieces if all you wanted was to destroy something huge. But that would be the equivalent of a stripper taking the stage and immediately ripping all her clothes off. The fun is in the tease: first L.A. goes, then Las Vegas, then other cities, then other countries, one at a time, over and over again — the stripper in this analogy was bundled up in a lot of clothing when she started — allowing the audience to savor each new cataclysm.

That kind of thing is fun, sure — I like watching stuff fall over as much as the next guy — but for crying out loud, the movie is 2 1/2 hours long. Most other movies aren’t that long, and most other movies have actual stories and characters to deal with. A hundred and fifty minutes of senseless mayhem, no matter how slickly produced, gets old after a while, and the plot contrivances required to keep things going become absurdly strained. There isn’t a lot in the way of real humor, either, unless you like jokes where a man says to his girlfriend, “I feel like there’s something separating us” and instantly an earthquake makes a huge crack appear in the ground between them. Then again, at least the film isn’t aggressively obnoxious or irritating, the way such destructo-porn often is in the hands of a Michael Bay or a Brett Ratner.

What is a little annoying, however, is the film’s final message, which is that humanity must work together in order to remain truly human. As some survivors have reached safety and close the gates on the stragglers, Adrian asks, “Can we really stand by and watch these people die?” That’s funny — I thought the whole reason this movie existed was so we could stand by and watch people die. Now you’re telling us we shouldn’t be enjoying it? Or does that not apply to “2012” because, after all, despite the endless devastation, very few individual deaths of individual people were actually shown? Billions of people die in “2012,” but mostly just by implication. I guess that lets us be entertained by it guilt-free. If we stand by and watch people die, though: naughty! Cover your eyes when you see a body! Focus only on the buildings!